II. Those With a Role in Liturgical Celebrations
13. Liturgical services are celebrations of the Church, that is, of the holy people united in proper order under a bishop or priest.  In a liturgical service the priest and his ministers have a special place because of holy orders; the servers, reader, commentator, and choir members, because of the ministry they perform. 
14. Acting in the person of Christ, the priest presides over the gathered assembly. The prayers he sings or recites aloud are spoken in the name of the entire people of God and of all the assembly;  therefore all present must listen to them with reverence.
15. The faithful carry out their proper liturgical function by offering their complete, conscious, and active participation. The very nature of the liturgy demands this and it is the right and duty of the Christian people by reason of their baptism. 
This participation must be:
a. internal, that is, the faithful make their thoughts match what they say and hear, and cooperate with divine grace; 
b. but also external, that is, they express their inner participation through their gestures, outward bearing, acclamations, responses, and song. 
The faithful are also to be taught that they should try to raise their mind to God through interior participation as they listen to the singing of ministers or choir.
16. A liturgical celebration can have no more solemn or pleasing feature than the whole assembly's expressing its faith and devotion in song. Thus an active participation that is manifested by singing should be carefully fostered along these lines:
a. It should include especially the acclamations, responses to the greetings of the priest and the ministers and responses to the litanies, the antiphons and psalms, the verses of the responsorial psalm, and other similar verses, hymns, and canticles. 
b. Pertinent catechesis as well as actual practice should lead the people gradually to a more extensive and indeed complete participation in all the parts proper to them.
c. Some of the congregational parts may be assigned to the choir alone, however, especially when the people are not yet sufficiently trained or melodies for part-singing are used. But the people are not to be excluded from the other parts proper to them. The practice of assigning the singing of the entire Proper and Ordinary of the Mass to the choir alone without the rest of the congregation is not to be permitted.
17. At the proper times a holy silence is also to be observed.  That does not mean treating the faithful as outsiders or mute onlookers at the liturgical service; it means rather making use of their own sentiments to bring them closer to the mystery being celebrated. Such sentiments are evoked by the word of God, the songs and prayers, and the people's spiritual bonds with the priest as he recites the parts belonging to the celebrant.
18. Those of the faithful who are members of religious societies for the laity should receive special training in sacred song, in order that they may make an effective contribution to sustaining and furthering the congregation's participation.  But the training of all the people in this regard is to be carried out thoroughly and patiently as part of their complete liturgical formation. It should be suited to their age, condition, way of life, and stage of religious development and should begin from the very first years of their schooling in the primary grades. 
19. Because of the liturgical ministry it exercises, the choir (capella musica, schola cantorum) should be mentioned here explicitly.
The conciliar norms regarding reform of the liturgy have given the choir's function greater prominence and importance. The choir is responsible for the correct performance of the parts that belong to it, according to the differing types of liturgical assembly and for helping the faithful to take an active part in the singing.
a. Choirs are to be developed with great care, especially in cathedrals and other major churches, in seminaries, and in religious houses of study.
b. In smaller churches as well a choir should be formed, even if there are only a few members.
20. Over the centuries the choirs of basilicas, cathedrals, monasteries, and other major churches have won high praise because they have preserved and developed the priceless treasury of sacred music. By means of rules issued specifically for them and reviewed and approved by the Ordinary such choirs are to be continued in order to carry out liturgical celebrations with greater solemnity.
Nevertheless choir directors and parish priests (pastors) or rectors of churches are to ensure that the congregation always joins in the singing of at least the more simple parts belonging to them.
21. Especially where even a small choir is not possible, there must be at least one or more cantors, thoroughly trained to intone at least the simpler chants that the congregation sings and to lead and sustain the singing.
Even in churches having a choir it is better for a cantor to be present for those celebrations that the choir cannot attend but that should be carried out with some degree of solemnity and thus with singing.
22. Depending on the established customs of peoples and on other circumstances, a choir may be made up of men and boys, of all men or all boys, of both men and women, and, where the situation really requires, even of all women.
23. According to the design of the particular church, the place for the choir is to be such that:
a. its status as a part of the community with a special function is clearly evident;
b. the performance of its liturgical ministry is facilitated; 
c. full, that is, sacramental, participation in the Mass remains convenient for each of the members.
When there are women members, the choir's place is to be outside the sanctuary.
24. In addition to musical training, choir members should receive instruction on the liturgy and on spirituality. Then the results of the proper fulfillment of their liturgical ministry will be the dignity of the liturgical service and an example for the faithful, as well as the spiritual benefit of the choir members themselves.
25. Diocesan, national, and international associations for sacred music, especially those approved and repeatedly endorsed by the Apostolic See, are to offer help for both the artistic and spiritual training of choirs.
26. The priest, ministers, servers, choir members, and commentator are to sing or recite the parts assigned to them in a fully intelligible way, in order to make it easier and obvious for the congregation to respond when the rite requires. The priest and the ministers of every rank should join their own voices with those of the entire assembly in the parts belonging to the congregation.